1. Field of the Invention
This invention relates to a process for the hydrolysis of acetals to the corresponding aldehydes and alcohols and, more particularly, to a direct, simple method for the selective hydrolysis of acetal to acetaldehyde and methanol in the presence of a variety of other reaction effluent components, typically those resulting from the reductive carbonylation of an alcohol feedstock, e.g., methanol.
2. Description of the Prior Art
Homologation reactions typically involve the reaction of a selected alcohol with carbon monoxide and hydrogen under elevated temperatures and superatmospheric pressures, in the presence of a suitable catalyst, e.g., a metal carbonyl complex. In the reductive carbonylation of methanol, the resulting reaction effluent contains a substantial amount of acetal byproduct, e.g., dimethoxy ethane, acetaldehyde diethylacetal and the like, as well as unreacted methanol, acetaldehyde and ethanol, together with water, methyl acetate, catalyst and a solvent. Similar effluents have been treated in the prior art by heating the solution in aqueous acid, or in the presence of another suitable catalyst, to catalyze the hydrolysis of the resulting acetal in order to obtain the desired products, acetaldehyde and alcohol. Typical of such systems is U.S. Pat. No. 4,388,154, which discloses a process wherein acetaldehyde and methanol are obtained from reaction effluents of the homologation of methanol and which, in addition to acetaldehyde, contain acetaldehyde dimethylacetal, methanol, methyl acetate, water and catalyst. The problem with such a process is that the chosen hydrolysis catalyst, e.g., an acid, fosters competing unwanted side reactions with the acetal and/or aldehyde. Also, almost all catalysts are acidic in nature, and usually facilitate corrosion by their presence in the reaction zone. Finally, the prior art systems have a tendency to hydrolyze any esters present in the system, e.g., the presence of the catalyst enhances the saponification of the esters and can lead to the formation of products such as acetic acid, which greatly complicates the ensuing recovery of the desired components present in the system.
Accordingly, it is an object of the present invention to provide a process for the effective, yet simple and selective hydrolysis of acetals while in the presence of a wide variety of other reaction components.
It is another object of the invention to provide a process for the hydrolysis of dimethoxy ethane to acetaldehyde and methanol in an effluent stream resulting from the reductive carbonylation of methanol.
It is still another object of this invention to provide a process for the hydrolysis of acetal which is formed during the reductive carbonylation of methanol, which process substantially eliminates unwanted side reactions, is substantially corrosion-free, and proceeds at desired reaction rates.